This invention relates to a hydraulic circuit for a hydraulically driven vehicle and in particular to shuttle valves arrangements in the circuit.
A hydraulically driven vehicle is generally provided with a pair of variable displacement pumps driven by a common engine and a pair of variable displacement motors each connected with the respective variable displacement pumps in a closed loop circuit and driven thereby. Each the closed loop circuit has connected in parallel therewith a shuttle valve.
Both the shuttle valves are connected with each other and with a fixed displacement charge pump driven by the common engine. However, since the neutral position of such a conventional shuttle valve is not connected with the respective closed loop circuits, no connection is established between the both closed loop circuits when the both shuttle valves remain in their neutral positions. Therefore even when the vehicle is being stopped or parked with its engine running, there is a possibility for the vehicle to start creeping because the exact balance of both the closed loop circuits may not sometimes be obtained in the case that the complete zero of the displacement of both the variable displacement pumps are not established.